In the field of arc welding, the five (5) main types of arc welding are submerged arc welding (SAW), shielded metal arc welding (SMAW), flux-cored arc welding (FCAW), gas metal arc welding (GMAW), and tungsten arc welding (TIG). In submerged arc welding, coalescence is produced by heating with an electric arc between a bare-metal electrode and the metal being worked. The welding is blanketed with a granular or fusible material or flux. The welding operation is started by establishing an arc beneath the flux to produce heat to melt the surrounding flux so that it forms a subsurface pool which is kept fluid by the continuous flow of current. The end of the electrode and the work piece directly below it become molten and molten filler metal is deposited from the electrode onto the work. The molten filler metal displaces the flux pool and forms the weld.
In the art of welding, much prior effort has been expended in developing flux compositions of the type having predetermined flux components intended to perform in predetermined manners. A large number of compositions have been developed for use as fluxes in arc welding both for use generally as welding fluxes and for use as a coating on a metallic core or within a sheath. Fluxes are utilized in arc welding to control the arc stability, affect the flow of molten metal, modify the weld metal composition, and provide protection from atmospheric contamination. Arc stability can be at least partially controlled by modifying the composition of the flux. It is therefore desirable to have substances which function well as plasma charge carriers in the flux mixture. Fluxes also modify the weld metal composition by rendering impurities in the metal more easily fusible and providing substances which these impurities may combine with in preference to the metal to form slag. Practically all slag-forming compounds may be classed as either acidic or basic, according to which compounds they react with. The substances which are considered to be the most active “bases” are those which are compounds of the elements forming basic compounds in ordinary chemical reactions in water solutions, such as calcium, magnesium, and sodium. The most common active “acid” substances are compounds of silicon, titanium, zirconium and aluminum. Fluxes are prepared with a higher or lower percentage of acidic or basic compounds, depending on the type of metal to be welded and impurities in the metal, the welding application, and/or the desired mechanical properties of the weld bead. In some instances, other materials may be added to lower the slag melting point, to improve slag fluidity, and to serve as binders for the flux particles.
The present invention is particularly directed to a submerged arc welding flux which exhibits improved impact strength, improved slag detachability, inhibits hydrogen absorption in the weld metal and/or improves the formation of a weld bead.